Casting pewter and making molds

Picture is here

i

Yes. It's very easy.

I've never tried it, but it should be OK, unless there is a surface alloying problem. Pewter is around 90% tin. Maybe Ted Frater will know if there's any problem casting it in aluminum.

I've cast it in open, oven-dried (but not calcined) Plaster of Paris molds. I made medals out of it for my sports car club when I was in high school. I melted it with a propane stove in an old stainless pot. Like you, I started with an old souvenir plate.

My crude casting process was risky, but it worked.

It is possible they are real pewter, but most "pewter" is really brittania metal, which is mostly tin and contains no lead.

This is what I mean, 90%+ of tin and no lead. I do not like lead (despite having 50+ lbs of lead ingots, that I melted from gun range floor sweepings). Lead is unhealthy and very dirty. Everything it touches, it marks with lead residue.

i

I've cast a number of items in pewter, Britannia metal actually these days, but have not tried in aluminium moulds. I typically carve a master in aluminium and then form a two part mould by pouring Dow Corning 3120 catalysed with BC catalyst for increased flow. The 3120 is a RTV silicone which can withstand higher temperature and although it's not rated for the pour temperature of the pewter it does stand up for limited use very well. My understanding is that for longer runs a master would be done this way and then further moulds made from that using a heat vulcanised silicone that'll withstand increased use. I don't know about the US but in the UK Alex Tiranti do suitable materials in small quantities.

The pewter sheet I normally form is 92-6-2, ie 92% tin, 6% antimony, and

2% copper. A casting alloy would usually have a higher percentage of antimony as it counters shrinkage when the metal solidifies.

Never done it with Al molds. I used to use two part silicone rubber, most any kind will work. The stuff made for pewter casting probably lasts longer. Karl

Guy I know cast pewter a fair amount, using soapstone molds. But he was probably deliberately trying to do it as "old fashioned" as possible. Anyway, worked fine.

If you stumble across bulk lots of lead-free solder in your auctioneering, it comes pretty close to being "pewter" for many purposes, though it's neither old-fashioned leaded pewter nor Britannia metal. Still, 95-5 solder (AKA, good old fashioned "lead free") only lacks 2% of copper to be Britannia metal...

You can probably auctioneer yourself a solder pot while you are at it, except I suspect you enjoy the idea of cooking it on your grill.

What is the working temperature of the pewter or Brittannia metal? If it's not much more than pure lead, wheel weight alloy, or linotype lead there really should be no issue with aluminum molds. The tackle guys make lead spinnerbaits, jigs, buzzbaits, and sinkers in aluminum molds all the time. They do flux the lead if they are unsure of its content or how clean it is. I also used to make my own bullets out of pure lead (as pure as I could get) in an aluminum mold when I shot black powder regularly. No issues there either. I made my own crappie jigs in cast and then machined aluminum molds also, and I have made a couple spinnerbait molds out of aluminum that are in small scale production.

I guess the answer is how much hotter do you have to get your pewter to get it to flow well.

If you do make aluminum molds you will definitely need to use a releasing agent on the molds. A cheap easy release agent is candle smoke, but if you do a lot you may want to look at Franklin's releasing agent for aluminum molds.

(other materials in aluminum molds may not need a releasing agent.)

Nothing major, 200C or so. Even less than lead, IIRC.

Exactly what I wanted to know.

I think that there is some mold release spray that I could use.

i

I've cast a vee block of 95/5 solder in a wooden mold. The wood chars slightly but not seriously for one piece.

The casting sand I got from an iron foundry holds small details in

95/5 quite well.

jsw

Ecnerwal on Mon, 13 Jun

2011 07:27:26 -0400 typed in rec.crafts.metalworking the following:

Hmm, how can I add that 2$ copper to the alloy? (Melting temp of copper vs solder, and all that.)

In most cases in which a higher-melting-temp metal is alloyed with a lower-temp metal (copper into zinc, for brass, as an example), you melt the lower-temp metal and then place pieces of the higher-temp metal into it. As strange as it sounds, the higher-temp metal will melt into it, as it forms a low-temp alloy at the interface.

It's probably the same thing with pewter.

I have cast with the "lead Free " pewter into plaster (baked, but not calcined), aluminum, steel, stone, wood and clay. All without problems

and SIlicone Rubber ) with minor problems.

Just make sure you have no undercuts, and do have positive draft on big pieces.

Ignoramus21268 wrote:

jk

It is.

You can just put the copper into the molten pewter, and keep it agitated, When I did this, I used electrical copper wire, and just stirred the pot with it until it dissolved away.

In essence it is like dissolving sugar (which has a higher melting point than water) in water.

jk

It is dissolved by the molten metal, it does not melt. Much like sugar dissolves in water, in fact. It's the same principle used in assaying, where molten lead dissolves metals that melt at temperatures beyond that of the molten lead (which comes from added litharge). Molten metals are very strong solvents of other metals (something you learn when you refine precious metals as I've done).

Harold

Neat. Now to get some of that lead free solder - I've bunches of scrap copper. (actually, I want the free lead solder, I can fake the rest ...)

pyotr